Descending cascade, a force in the north (9)
I believe the answer is:
waterfall
I believe this is a triple definition!
'descending' is the first definition.
(thesaurus)
'cascade' is the second definition.
(synonyms)
'a force in the north' is the third definition.
(I've seen this before)
(Other definitions for waterfall that I've seen before include "Cataract" , "source of power, possibly a force in the north" , "Cascade, force" , "One of the aqueous drops" , "Drop of Adam's ale" .)